2005-2008 Honda ATV TRX500FA/FGA Fourtrax, Rubicon Factory Service Manual, Page 81Get this manual
MAINTENANCE The oil tank contains sufficient amount of oil if the oil level is between the upper and lower level marks on the dipstickDIPSTICK UPPER LEVEL
LOWER LEVEL If the oil level is near or below the lower level mark, remove the oil filler cap and add the recommended engine oil up to the upper level markOIL FILLER CAP
RECOMMENDED ENGINE OIL: Pro Honda GN4 4-stroke oil or equivalent motor oil API service classification: SG or higher JASO 903 standard: MA Viscosity: SAE 10W-30